The invention also relates to improvements to electric supply devices capable of delivering without interruption AC electric energy to a load, comprising:
a transformer having a secondary assembly connectable to the load to be supplied with power,
first means for connecting to a main AC electric source, these first connection means being connected to the primary assembly of the transformer,
second means for connecting to an auxiliary DC electric source, these second means being connected to power oscillator means themselves connected to the primary assembly of the transformer,
means for detecting a failure of the main source,
control means, placed under the dependence of said detection means, for selectively controlling the supply to the primary assembly of the transformer of power either from the main source when this is in an operating condition, or from the auxiliary source when the main source has failed (cut-off),
and synchronizing means associated with said control means for synchronizing the switching of the supply from one source to the other so that no discontinuity results therefrom in the AC supply of the load.
Different devices of this type are already known which, however, are of complex design and consequently expensive to manufacture.